In these patients, a reduction in salt intake led to a significant fall in blood pressure and urinary albumin excretion, a marker of cardiovascular disease. The reduction in urinary albumin excretion may carry additional benefits in reducing cardiovascular disease above the effects on blood pressure.
The number of people diagnosed with diabetes in the UK is currently estimated to be 3.5 million, 90 per cent of which have type 2 diabetes. Raised blood pressure is one of the most important risk factors in type 2 diabetes, with at least a twofold increased risk in developing cardiovascular disease compared to those who do not have type 2 diabetes or glucose intolerance.
The study, published in Hypertension, looked at 46 individuals with type 2 diabetes or impaired glucose tolerance and normal or mildly raised blood pressure. Patients were randomised either to take salt tablets (5g salt/day), or the equivalent number of placebo tablets (0g salt) for six weeks. At the end of the six week period the participants crossed over to take the opposite tablets for a further six weeks. Blood pressure was measured before entry to the study and at the end of each six week period.
Study co-author Graham MacGregor, Professor of Cardiovascular Medicine at QMUL and Chairman of Consensus Action on Salt & Health said: "This study clearly demonstrates that salt reduction is effective in lowering blood pressure in patients with type 2 diabetes or glucose intolerance. This is the first time that this has been so conclusively demonstrated and it is important now that all patients with type 2 diabetes or glucose intolerance are given appropriate advice on how to reduce their salt intake.
"This study also has public health implications in that it is vital that we continue to reduce salt intake in the UK by getting the food industry to take out the huge and completely unnecessary amounts of salt that they put into our food."
Dr Rebecca Suckling, Consultant Nephrologist at St Helier Hospital and lead author of the research, said: "This study is the first and largest study of dietary salt intake in patients with type 2 diabetes or impaired glucose tolerance early on in their disease and has shown that lowering salt intake reduces blood pressure and the urinary albumin level, both important risk factors for cardiovascular disease and kidney failure."
"Reducing blood pressure through lifestyle changes is recommended by all national and international guidelines but patients do not consistently receive any advice on lowering salt intake. This study highlights that all patients with type 2 diabetes and impaired glucose tolerance should be given advice on lowering salt intake to levels at least less than 6g a day."
Explore further: Gene study could help heart patients cut craving for salt
Rebecca J. Suckling et al. Modest Salt Reduction Lowers Blood Pressure and Albumin Excretion in Impaired Glucose Tolerance and Type 2 Diabetes Mellitus, Hypertension (2016). DOI: 10.1161/HYPERTENSIONAHA.115.06637